The UK High Court has handed down its decision on whether a prodrug can itself constitute the “active ingredient” protected by a supplementary protection certificate (SPC), even where it is pharmacologically inactive before being metabolised in the body.

In Aristo Pharma GmbH v Takeda Pharmaceuticals USA Inc [2026] EWHC 2414 (Pat), His Honour Judge Hacon upheld Takeda’s SPC for lisdexamfetamine (LDX).

This decision is particularly relevant to businesses developing prodrugs or other derivatives of previously authorised active substances and provides further guidance on the relationship between the regulatory identification of an active substance and the “product” protected by an SPC.

What was the issue?

Takeda markets LDX under the name Elvanse for the treatment of ADHD.

LDX is a prodrug consisting of lysine covalently bound to dexamfetamine (DEX) that is inactive when administered. In the body, the bond between lysine and DEX is hydrolysed, releasing DEX into the bloodstream. DEX provides the pharmacological activity responsible for treating ADHD.

Importantly, DEX had already been authorised as a medicinal product before Elvanse. The validity of Takeda’s SPC therefore depended on which substance constituted the relevant “product” under the SPC Regulation.

If the product was LDX, the Elvanse marketing authorisation supported the SPC. If the product was instead DEX, that authorisation was not the first marketing authorisation for the product and the SPC would not meet the requirements of Article 3(d).

What did the High Court decide?

The court concluded that LDX is the relevant “active ingredient” and therefore the “product” for SPC purposes.

A central issue was whether a substance described as pharmacologically inactive could nevertheless constitute an active ingredient. The court considered earlier case law from the Court of Justice of the European Union (CJEU) . This included Forsgren (C-631/13), which states that an active ingredient must have a pharmacological, immunological or metabolic action of its own. However, the court distinguished a prodrug such as LDX from a known active ingredient combined with a non-active carrier or excipient as was the case in the Forsgren decision. LDX is a single new molecule, albeit one which is metabolised after administration to release DEX.

The court also considered the properties of LDX compared with DEX. The slower and more prolonged release of DEX following administration of LDX permits once-daily dosing, whereas DEX requires multiple doses. The court regarded these different pharmacokinetic characteristics and their clinical consequences as relevant to the assessment.

The regulatory treatment of LDX was also particularly significant. HHJ Hacon concluded that the test for an “active substance” under the medicinal products legislation is the same as the test for an “active ingredient” under Article 1(b) of the SPC Regulation. The Elvanse marketing authorisation identified LDX as its active substance.

This also brought the court to the pending referral to the CJEU in the case of Halozyme (C-456/24). In that case, Advocate General Emiliou recently provided their opinion that an SPC authority should follow the classification adopted through the regulatory process rather than independently reassessing whether a substance identified as an excipient should instead be regarded as an active ingredient.

HHJ Hacon described the Advocate General’s reasoning as “compelling”. However, he did not need to determine whether the regulatory classification must always be treated as conclusive, because he considered that LDX qualified as the active ingredient even if the issue were to be reassessed under the existing CJEU case law.

Why is the decision important?

The decision confirms that a prodrug is not excluded from SPC protection simply because it is pharmacologically inactive before metabolism or because it ultimately releases a previously authorised active substance.

It also reinforces the growing importance of the regulatory documentation when assessing SPC validity, which was also considered in the Accord v Novartis decision albeit in the context of a product rather than an active ingredient. In particular, how a new molecule is characterised in the marketing authorisation, together with its pharmacological and pharmacokinetic properties, may ultimately be critical to whether additional SPC protection is available. This issue is particularly topical given the pending Halozyme judgment, which may provide further CJEU guidance on whether SPC authorities can look beyond the regulator’s classification of a substance.

The decision is also notable because courts and patent offices across Europe have failed to adopt a uniform approach on this issue. In particular, the German Federal Patent Court reached a different conclusion concerning the equivalent German SPC, whereas decisions in a number of other jurisdictions have followed the same approach as the UK High Court and upheld the SPC.

Case details at a glance

Jurisdiction: England & Wales
Decision level: High Court
Parties: Aristo Pharma GmbH v Takeda Pharmaceuticals USA Inc and Takeda Pharmaceuticals International AG, and between Stada Arzneimittal AG and Takeda Pharmaceuticals USA Inc
Date: 24 September 2026
Citation: [2026] EWHC 2414 (Pat)
Decision: https://dycip.com/2026-ewhc-2414-pat